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http://www.sciencedaily.com/releases/2008/04/

080424120953.htm

Autism Risk Linked To Distance From Power Plants, Other Mercury-releasing
Sources

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Is the risk of autism greater for children who live closer to the
pollution source? (Credit: iStockphoto/Marcin Pawinski)ScienceDaily
(Apr. 25, 2008)  How do mercury emissions affect pregnant mothers,
the unborn and toddlers? Do the level of emissions impact autism rates? Does
it matter whether a mercury-emitting source is 10 miles away from families
versus 20 miles? Is the risk of autism greater for children who live closer
to the pollution source?

A newly published study of Texas school district data and industrial
mercury-release data, conducted by researchers at The University of Texas
Health Science Center at San Antonio, indeed shows a statistically
significant link between pounds of industrial release of mercury and increased
autism rates. It also showsfor the first time in scientific
literaturea statistically significant association between autism risk
and distance from the mercury source.

This is not a definitive study, but just one more that furthers the
association between environmental mercury and autism, said lead author
Raymond F. Palmer, Ph.D., associate professor of family and community medicine
at the UT Health Science Center San Antonio. The article is in the journal
Health & Place.

Dr. Palmer, Stephen Blanchard, Ph.D., of Our Lady of the Lake University
in San Antonio and Robert Wood of the UT Health Science Center found that
community autism prevalence is reduced by 1 percent to 2 percent with each
10 miles of distance from the pollution source.

This study was not designed to understand which individuals in the
population are at risk due to mercury exposure, Dr. Palmer said.
However, it does suggest generally that there is greater autism risk
closer to the polluting source.

The study should encourage further investigations designed to determine the
multiple routes of mercury exposure. The effects of persistent, low-dose
exposure to mercury pollution, in addition to fish consumption, deserve
attention, Dr. Palmer said. Ultimately, we will want to know
who in the general population is at greatest risk based on genetic
susceptibilities such as subtle deficits in the ability to detoxify heavy
metals.

The new study findings are consistent with a host of other studies that confirm
higher amounts of mercury in plants, animals and humans the closer they are
to the pollution source. The price on children may be the highest.

We suspect low-dose exposures to various environmental toxicants, including
mercury, that occur during critical windows of neural development among
genetically susceptible children may increase the risk for developmental
disorders such as autism, the authors wrote.

Study highlights

Mercury-release data examined were from 39 coal-fired power plants and 56
industrial facilities in Texas.

Autism rates examined were from 1,040 Texas school districts.

For every 1,000 pounds of mercury released by all industrial sources in Texas
into the environment in 1998, there was a corresponding 2.6 percent increase
in autism rates in the Texas school districts in 2002.

For every 1,000 pounds of mercury released by Texas power plants in 1998,
there was a corresponding 3.7 percent increase in autism rates in Texas school
districts in 2002.

Autism prevalence diminished 1 percent to 2 percent for every 10 miles from
the source.

Mercury exposure through fish consumption is well documented, but very little
is known about exposure routes through air and ground water.

There is evidence that children and other developing organisms are more
susceptible to neurobiological effects of mercury.

Implications

We need to be concerned about global mercury emissions since a substantial
proportion of mercury releases are spread around the world by long-range
air and ocean currents, Dr. Palmer said. Steps for controlling
and eliminating mercury pollution on a worldwide basis may be advantageous.
This entails greener, non-mercury-polluting technologies.

The U.S. Environmental Protection Agency (EPA) estimated environmental mercury
releases at 158 million tons annually nationwide in the late 1990s, the time
period studied by the Texas team. Most exposures were said to come from
coal-fired utility plants (33 percent of exposures), municipal/medical waste
incinerators (29 percent) and commercial/industrial boilers (18 percent).
Cement plants also release mercury.

With the enactment of clean air legislation and other measures, mercury
deposition into the environment is decreasing slightly.

Limitations

Dr. Palmer and his colleagues pointed out the study did not reflect the true
community prevalence rates of autism because children younger than school
age are not counted in the Texas Education Agency data system. The 1:500
autism rates in the study are lower than the 1:150 autism rates in recent
reports of the U.S. Centers for Disease Control and Prevention.

Furthermore, the authors note that distance was not calculated from individual
homes to the pollution source but from central points in school districts
that varied widely in area.

Data sources

Data for environmentally released mercury were from the United States
Environmental Protection Agency Toxics Release Inventory. Data for releases
by coal-fired power plants came from the same inventory and from the Texas
Commission for Environmental Quality. Data for school district autism came
from the Texas Education Agency.